Reference Circuit 446

REP015: Dual-Path CDMA PA Tuned for High Linearity




Objective: To develop a cellular CDMA PA application circuit with very high linearity and moderately good power-added efficiency (PAE).

Rapid Engineering Prototypes are real circuits that Maxim application engineers have built and measured in our labs. They can provide a starting point for new RF designs. They are not available as evaluation kits.


The MAX2264 high-power amplifier path was characterized and tuned to meet the following performance at narrowband CDMA: at a Pout of +28dBm, obtained 26.8dB gain, 28% efficiency, ACPR1 = -48.5dBc, and ACPR2 = -59.0dBc. This performance is fairly deep into linear mode, as the lowered PAE of 28% reflects. Typically, the part would be tuned for better than 33% efficiency and at least -44dBc ACPR1. The EV board was used for these tests.

The MAX2264 linear RF power amplifier is designed for U.S. cellular-band IS-98-based CDMA, PDC, and IS-136-based TDMAmodulation formats. For best low-power PAE, the MAX2264 offers a switched dual-path amplifier arrangement with an on-chipswitch. Statistically, CDMA handsets operate most of the time in a low-powered path (around +16dBm output), which is where PAE needs to be optimized. The MAX2264 offers typically 12% PAE at low power.

Block diagram of the transmit-path application
Schematic of the MAX2264 evaluation kit (PDF, 24kB)
Measurement test setup

 
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MAX2264
2.7V, Single-Supply, Cellular-Band Linear Power Amplifiers

  • Low Average CDMA Current Consumption in Typical Urban Scenario
  • 0.5µA Shutdown Mode Eliminates External Supply Switch
  • ±0.8dB Gain Variation Over Temperature